The present invention relates to a finned tube useful for heat exchangers and more particularly to a novel construction of a tubing helically wound with a crimped fin.
The present invention also relates to a method for fabricating a novel finned tube.
A number of types of finned tubing, a length of which is helically wound with a thin strip of heat-radiating material, are well known. The periphery of the fin must be stretched in order to wind the fin around the tubing with no crimps are provided. In this instance the tubing can not be a thin tubing since the tubing must tolerate the higher pressure which is caused during the winding operation. Thus, the periphery of the strip may be ruptured when the fin is substantially long.
To avoid the above-mentioned defects, a fin having a number of cuts was proposed in the U.S. Pat. No. 3,134,166, Herbert J. Venables III "MANUFACTURE OF HEAT EXCHANGE TUBING", issued on May 26, 1964. However, it was discovered that cuts may be undesirably bent or torn off and may considerably increase ventilating resistance.
It was proposed to provide transverse crimps on the strip in the U.S. Pat. No. 1,972,230, Edward G. Lehman "FINNED TUBE", issued on Sept. 4, 1934. However, the strip could not achieve close contact with the periphery of the tubing since only one edge of the strip, which is very thin, contacts the periphery of the tubing.
U.S. Pat. No. 2,532,239, John Shipley Newlin "FINNED TUBE WINDING MACHINE", issued on Nov. 28, 1950 suggested providing flutes along one edge of the strip and depress them against the periphery of the tubing during the winding operation in order to provide a base for making good contact with the tubing. In this instance the tubing must be thick since the flutes are flattened by depressing them against the tubing and the contacting area can not be selected without regard to the height of the fin.